The present invention relates to an induction manifold for an internal-combustion engine.
In internal-combustion engines it is known to use systems for recirculating gas from the exhaust to the intake (abbreviated in the following to EGR systems, which is the acronym for xe2x80x9cexhaust gas recirculationxe2x80x9d), for the purpose of reducing the content of nitrogen oxides (NOx) in the exhaust gases.
An important requirement, which is to be met by EGR systems so as to ensure proper operation of the internal-combustion engine, is to supply to the various cylinders a homogeneous mixture of recirculated air and exhaust gases (in the following xe2x80x9cEGR gasesxe2x80x9d). In fact, it is known that inhomogeneous mixing of the EGR gases with the air results in unsatisfactory combustion, with consequent smoky exhaust and emission of particulates.
Known EGR systems normally comprise a recirculation tube connecting the exhaust manifold of the engine to the induction manifold via a flow-control valve. The admission of the EGR gases takes place at the inlet of the induction manifold so as to ensure satisfactory mixing in the manifold itself before admission into the cylinders. However, this involves an increase in the amount of space occupied.
The object of the present invention is to produce an induction manifold for an internal-combustion engine, which makes it possible to obtain proper mixing of the EGR gases with the air and which, at the same time, is of reduced dimensions and can be produced simply and economically.
Therefore, in accordance with the invention there is devised an induction manifold for an internal combustion combustion engine, comprising an elongate main body provided with longitudinal inner cavity adapted to communicate, in operation, with a plurality of intake orifices of the engine, an inlet duct provided with an air-inlet opening and communicating with said cavity, and means for feeding EGR gases into said inlet duct, characterised in that said means for feeding EGR gases comprise a feed duct formed integrally with said manifold and comprising a first portion extending inside said main body and provided with an inlet orifice for EGR gases at one end of said main body, and a second portion extending inside said inlet duct and provided with an outlet opening in said inlet duct, and baffle means interposed between said air-inlet opening of said inlet duct and said outlet opening of said feed duct for directing the air and said EGR gases towards a mixing zone inside said inlet duct and situated at a predetermined distance from said cavity of said main body.